Process for controlling the couplings of a hydrostatic and mechanical torque division gearing

Abstract

A method of changing the range of a hydrostatic/mechanical power split transmission is specified: firstly, the command to engage the clutch for the next range is given, then the transfer of the load to this clutch is carried out and then the command to disengage the clutch for the old range (V x ) is given if, during the load transfer, a characteristic speed value of the summing planetary gearbox (10), for example the speed of the planet carrier (25), remains constant. In this way, the sensors for the clutches are dispensed with and quicker changes of range are made possible.

I claim: 
     
       1. A method of controlling a hydrostatic/mechanical power split transmission, which comprises an adjustable hydrostat unit (4), a multiple shaft summing planetary gearbox (10; 15) for combining the mechanical path and hydrostatic path, and a step gearbox (11; 16) connected downstream in order to form "n" gear change ranges (V 1 , V 2 , . . . , V n ), which adjoin one another at synchronization points and are passed through by means of adjusting the hydrostat unit (4), it being the case that, at each change from an old range (V x ) to a next range (V x-1  ; V x+1 ), a) firstly, when the synchronization speed is reached, the command to engage the clutch for the next range (V x-1  ; V x+1  is given,   b) then the transfer of the load from clutch for the old range (V x ) to the clutch for the next range (V x-1  ; V x+1 ) is performed by adjusting the hydrostat unit, and   c) then the command to disengage the clutch for the old range (V x ) is given, wherein the command to disengage the clutch for the old range (V x ), is given only if, during the load transfer, a characteristic speed value of the summing planetary gearbox (10) remains constant.     
     
     
       2. The method of controlling a hydrostatic/mechanical power split transmission as claimed in claim 1, the summing planetary gearbox (10) having a sun wheel (20) driven by the hydrostatic path, an internal gear (21) driven by the mechanical path, and a planet carrier (25), wherein the characteristic speed value is the speed of the planet carrier (25). 
     
     
       3. The method of controlling a hydrostatic/mechanical power split transmission as claimed in claim 1, the summing planetary gearbox (15) being a double planetary gearbox with a first input shaft (60) driven by the mechanical path, a second input shaft (65) driven by the hydrostatic path, and two output shafts (64, 71), each connected to an element in the double planetary gearbox, wherein the characteristic speed value is the difference between the speeds of the two output shafts (64, 71). 
     
     
       4. The method of controlling a hydrostatic/mechanical power split transmission as claimed in claim 1, wherein, if the characteristic speed value of the summing planetary gearbox (10; 15) changes during the load transfer, the command to disengage the clutch for the old range (V x ) is not given, the engage command for the next clutch is withdrawn and the hydrostat unit (4) is adjusted again in the direction of a transfer of the load to the clutch for the old range (V x ). 
     
     
       5. The method of controlling a hydrostatic/mechanical power split transmission as claimed in claim 4, wherein, after the load has been transferred to the clutch for the old range (V x ), the range change is repeated with the command to engage the clutch for the next range (V x-1  ; V  x+1 ).